Computer systems employing multiple individual computers, processors, or nodes may employ some type of quorum programming, wherein a majority of the individual computers determines membership in the computer system. Thus, a majority of computers may determine to admit or remove an individual computer from membership in the computer system. In this scheme, a computer that is removed is deactivated; a computer that is admitted is activated. The individual computers may determine membership on a periodic basis, and that basis may be based on regular intervals (e.g., every minute) or on episodic events (e.g., computer system powered up).
Computer systems comprising multiple individual computers also are known to employ various protocols and communications techniques so that an individual computer can track the health of the other computers in its computer system. These protocols typically involve sending periodic health messages (e.g., heartbeats) to the other computers in the computer system, or to a central computer. However, these protocols may only work well in the presence of a total and abrupt failure of a computer within the computer system. These protocols are not able to detect and compensate for other types of failures that likely occur in the computer system. Moreover, these protocols cannot guarantee that the correct (ideal) computer will be deactivated.